Project Summary/Abstract The major aim of the project is the first comprehensive historical examination of encephalitis lethargica (`sleeping sickness'), an unprecedented and aggressive encephalitis epidemic which swept the globe between the two World Wars. Two- thirds of the victims, predominantly between 10 and 30 years of age, survived the initial phase, but most developed severe `post-encephalitic'neurological syndromes. In particular, older patients developed post-encephalitic parkinsonism and other severe motor abnormalities, resulting in their being incapacitated for the remainder of their lives. Persons younger than 21 years of age developed a behavioural syndrome which resembled what is now described as `attention deficit syndrome', before they too succumbed to crippling parkinsonism. The cause of this catastrophe, largely forgotten despite huge costs in both human and economic terms, has never been established, although a temporal association with the influenza pandemic of 1918/19 has frequently been interpreted as evidence for a causal relationship between the two epidemics. Medico-historical techniques, current neurological awareness and social analysis have been applied in order to produce the first history of encephalitis lethargica, whereby insights into both its nature and into parkinsonism, one of the most frequent neurological disorders in our ageing population, will be explored. The monograph will discuss the following aspects of encephalitis lethargica: - definition of 'encephalitis lethargica'and distinction from similar disorders; - its first appearance in various parts of the world and its pattern of spread; - medical responses to the disorder, including attempted therapies; - attempts to explain the disorder by the medical community; - the impact of the disorder on medical research, especially with respect to neurology and psychiatry; - popular responses, especially as reflected in contemporary press coverage; - the social and economic impact of the disorder; - encephalitis lethargica in literature and popular culture; - evidence for the existence of encephalitis lethargica before and since the 1918-1930 epidemic. A complete picture of the disorder will thereby be presented for the first time, a complete and integrated account of one of the greatest public health catastrophes of the 20th century. In light of the possibility that such a disaster may recur without warning, and particularly because the previous outbreak was strongly associated with pandemic influenza, it would be prudent to have available a documented account of its most recent major appearance as a guide for the future.